Method and apparatus for safely conducting blasting operations



A. E. JUDD June 27, 1967 METHOD AND APPARATUS FOR SAF'ELY CONDUCTING BLASTING OPERATIONS Filed Dec. 15, 1965 INVENTOR. Aer/w? E. M000 BY I) z ATTORNEYS- United States Patent 3,327,629 METHOD AND APPARATUS FOR SAFELY CONDUCTING BLASTING OPERATIONS Arthur E. Judd, Cloudcroft, N. Mex., assignor to Spectrum Technology Incorporated, El Paso, Tex., a corporation of Texas Filed Dec. 15, 1965, Ser. lo. 514,072 1 Claim. (Cl. 102-23) ABSTRACT OF THE DISCLOSURE A method, system, and apparatus for conducting blasting operations which includes the step of measuring the level of radio frequency energy induced in conductors interconnecting a blasting machine and a detonator and a system and meter containing apparatus for making such a measurement is disclosed.

This invention relates to a method and device for promoting safety in a blasting operation wherein an explosive charge is fulminated by an electrical detonator, such as a blasting cap.

It is well known by those expert in the use of explosives that stray radio signals can prematurely detonate an electrical blasting cap. A premature detonation is caused by the reception of a signal by the wires connecting the blasting machine to the electric blasting caps. In effect, the wires act as an antenna and transmit the received signal to the cap sometimes detonating the explosive charge. It has been thought that close range radio transmissions of moderate power constitute the major safety hazard, with workmen or signs being used to insure minimal vehicular radio transmissions in the blasting area. Although it is thought that short range vehicular radio transmissions constitute the major safety hazard in this area, it is believed that a radio signal from a distant commercial radio station or other radio frequency source could prematurely detonate an explosive charge because of the length and configuration of the wires leading from the blasting machine to the explosives.

It is a primary object of the instant invention to promote safety in blasting operations by providing a method and apparatus for detecting the presence of electrical energy in the wires leading from the blasting machine toward the explosives prior to connecting the blasting machine-wire-explosive circuit.

Another object of the instant invention is to provide a method and apparatus for measuring the amount of electrical energy present in the wires and, in particular, at the precise point on the wires where the explosives would be later connected, in order to determine if the energy present will detonate electrical blasting caps or the like.

Still another object of the instant invention is to provide a,method of safe blasting whereby the blasting machine-wire-detonator circuit will be connected only after it is ascertained that no energy is present or that the energy present in the wires is insufiicient to fulminate the electric detonators.

A further object of the instant invention is to provide an extremely simple detector for radio waves in the environment described which may be inexpensively manufactured, inexpensively maintained and which is foolproof in operation.

A still further object of the instant invention is to provide a detector having as its major components an ammeter in parallel with a rectifier.

Still another object of the instant invention is to provide a method and apparatus for detecting and measuring 3,327,629 Patented June 27, 1967 radio wave energy in the wire leading from a blasting machine toward an explosive charge in which the detector is removed prior to blasting for later use.

Other objects and advantages, as well as the invention itself, reside in the combinations of elements and manipulative steps, arrangements of parts and manipulative steps, and features of construction and operation, all of which will be more fully pointed out hereinafter and disclosed in the accompanying drawing wherein there is shown a preferred embodiment of this inventive concept.

In the drawing:

FIGURE 1 is an organizational view of a blasting machine, wires and detector as shown during the energy detecting portion of the blasting operation of the instant invention;

FIGURE 2 is another organizational view of a blasting machine, wires and explosive charge illustrated at a time after the completion of the detecting portion and prior to the activation of the blasting machine;

FIGURE 3 is an enlarged view of the detector of the instant invention;

FIGURE 4 is a schematic view of the electrical circuit of the detector of FIGURE 3; and

FIGURE 5 is an enlarged cross-sectional view of a releasable holding means utilized to selectively connect the wires leading to the blasting machine with the detector.

Referring now to the drawing in detail, wherein like reference characters designate like elements throughout the several views thereof, and more particularly to FIG- URES l and 2, there is indicated generally at 10 a conventional blasting machine of the type that delivers an electric current by the depression of a handle 12, although the term blasting machine is intended to include any type of electrical energy source utilized to detonate explosives. A pair of electrical conductors or wires 14 connect blasting machine 10 to a detector shown generally at 16 for ascertaining the presence of electrical energy in wires 14 prior to the connection of wires 14 to an explosive charge shown generally at 18 including an electrical detonator 20, such as a blasting cap, and an explosive substance 22 such as trinitrotoluene, trinitrobenzene, trinitrophenol, ammonium nitrates, nitroglycerin, grain, powder, gelatins, pellets, cords, dynamite or the like.

As in any blasting operation, explosive substance 22 will be positioned in the desired location with wires 14 strung out from the situs of the explosive substance to a safe area where blasting machine 10 will be positioned. Detector 16 is preferably secured to wires 14 to ascertain the presence of electrical energy prior to the hookup of wires 14 to blasting machine 10 and prior to the positioning or hookup of detonator 20 on explosive substance 22, although it should be understood that the detecting step may be conducted at any time prior to the hookup of wires 14 to detonator 20. After it has been ascertained that the quantity of electrical energy within wires 14 is below a predetermined limit, which constitutes the minimum energy necessary to activate blasting caps 20, detonator 20 will be appropriately positioned and wires 14 will be connected to blasting machine 10. The activation of blasting machine 10, as by the depression of handle 12, will deliver electrical current through wires 14 to fulminate detonators 20 which in turn set .off explosive substance 22.

Referring now to FIGURES 3 to 5 inclusive, detector 16 is illustrated as including a sturdy strong housing shown generally at 24 to which is afiixed a U-shaped handle 26 and which houses the components of the energy detecting means of the instant invention.

Detector 16 includes a direct current ammeter or milliammeter shown generally at 28 which may be of any suitable type provided it is of relatively high sensitivity.

Arnmeter 28 includes a frame 30 secured by frictional fasteners 32 to top wall 34 of housing 24 and is provided with a transparent face 36 under which is positioned a scale 38 and a movable pointer 40. Scale 38 is preferably marked with suitable indicia 42 such as the line and Unsafe designation illustrated or a red band to indicate an unsafe energy level for the type electrical detonator being used. In the alternative, a suitable table may be provided to indicate unsafe energy levels corresponding to different types of detonators by which the operator may compare the milliampere reading determined from indicia 44 of scale 38.

An electrically conductive wire 46 is secured in a conventional manner to each terminal 48 of ammeter 28 and leads to a jack or releasable holding means designated generally at 50 extending through and insulated from end wall 52 of housing 24. A rectifier shown generally at 54 is connected to wires 46 in parallel with ammeter 28 between jacks 50 and ammeter 28 by a pair of branch lines 56. Rectifier 54 acts to change the alternating type current of radio waves in wires 14 to direct current for detection and measurement by ammeter 28. This is achieved by passing current in one direction and not in the other or passing a great deal more current in one direction than in the other. It will be readily apparent that the quantity of direct current flow through ammeter 28 will be directly proportional to the amount of alternating current energy in wires 14.

Although any type of rectifier may be utilized, it is preferred to use a solid state diode rectifier since it has characteristics of compactness, sturdiness, and the ability to convert wide ranges of alternating current into direct current and, in addition, is a passive device requiring no supplementary power source. This has been found particularly advantageous since the signals received by wires 14 may range from a few cycles per second to many hundreds of millions of cycles per second.

Jack 50 may be any conventional type and is illustrated in FIGURE as including a cylindrical interiorly threaded sleeve 58 secured intermediate its length by a collar 60 to end wall 52 of housing 24. Wire 46 may be afiixed to one end of sleeve 58 in any suitable manner, as by the illustrated set screw 62 or by soldering or the like. Sleeve 58 forms a pair of transverse aligned apertures 64 outwardly of end wall 52 for receiving a free end of wire 14. A thumb screw 66 is threadably received in sleeve 58 for selectively securing wire 14 in aperture 64.

It is now seen that there is herein provided an improved method and apparatus for safely conducting blasting operations having all of the objects and advantages of the instant invention and others, including many advantages of great practical utility and commercial importance.

Since many embodiments may be made of the instant inventive concept, and since many modifications may be made in the embodiment hereinbefore shown and described, it is to be understood that the foregoing is to be interpreted merely as illustrative and not in a limiting sense.

I claim:

In a method of conducting blasting operations in which a blasting machine which generates an electrical impulse is interconnected by a pair of conductors with a detonator, an improved method for more safely conducting said blasting operations which comprises the steps of:

connecting the conductors to the blasting machine;

measuring the level of radio frequency energy induced in at least one of said conductors to thereby give information to an operator relative to whether said circuit may safely be completed prior to the completion thereof; and then connecting the conductors to the detonator to complete a circuit between the blasting machine and the detonator.

References Cited UNITED STATES PATENTS 2,655,619 10/1953 Neal. 2,732,518 1/1956 Bricaud 317-8O 3,033,114 5/1962 Gieske et al 102-20 3,202,227 8/ 1965 Ezran 102--20 X 3,208,378 9/1965 Boop 102-216 X SAMUEL FEINBERG, Primary Examiner.

V. R. PENDEGRASS, Assistant Examiner. 

